Eye Piece Graticule (Micrometer)

Quick Answer: The Eye Piece Graticule (Micrometer) is a small glass disc engraved with a scale that sits inside a microscope eyepiece, so the scale appears in focus over the specimen. Once the eyepiece graticule has been calibrated against a stage micrometer, it is used to measure cells, fibres and other small objects.

How the Graticule Scale Works

The graticule disc rests at the field stop of the eyepiece, the plane where the objective forms its image. Because the scale and the specimen image lie in the same plane, both look sharp together, and the scale can be laid across a cell or pollen grain much as a ruler is laid across a drawing. The divisions have no fixed value in micrometres, though. Their value depends on the objective in use, so the disc becomes a measuring tool only after calibration.

Calibration uses a stage micrometer, a slide ruled with a scale of known length. With both scales in view, the user lines up a division on each and counts how many eyepiece divisions cover a known length on the stage scale. Dividing that known length by the count gives the value of one eyepiece division for that objective. The routine is repeated for every objective and the results are written on a card kept with the microscope.

Graticules are made in several patterns: a straight linear scale, crosshairs for centring, or a square grid for counting cells or particles. The micrometer form named in this listing normally means a linear scale. Discs also come in different diameters to suit the eyepiece they sit in, so give the make or eyepiece type of your microscope when ordering.

Specifications

Applications

• Measuring cells, nuclei, pollen grains or starch grains in biology practicals
• Estimating fibre diameters in textile or forensic science teaching
• Following the growth of fungal hyphae or root hairs over several days
• Comparing cell sizes across tissues, such as guard cells against epidermal cells

Care & Handling

• Handle the graticule disc by its edges only, or with plastic-tipped tweezers, because a fingerprint on it will show in focus across the field of view.
• Unscrew the eyepiece over a soft cloth when fitting the disc, so it cannot fall onto a hard bench.
• Remove dust with a blower brush before wiping; a dry wipe drags grit across the etched lines.
• Keep the calibration card with the microscope and recalibrate whenever an eyepiece or objective is changed.

Why Choose LabEquip

Teachers setting up cell-measurement practicals, and college labs running microbiology or histology courses, are the usual buyers of graticules. They are listed in the Microscope & Optics range alongside the stage micrometer needed to calibrate them; share your eyepiece type on the contact page so LabEquip can match the disc.

Frequently Asked Questions

What is the difference between an eyepiece graticule and a stage micrometer?

The eyepiece graticule sits inside the eyepiece and carries an uncalibrated scale used for measuring. The stage micrometer is a slide with a scale of known length that sits on the stage and is used only to work out what each graticule division is worth.

Why do I have to recalibrate for each objective?

The objective magnifies the specimen but not the graticule, which is already in the eyepiece. Switching from low to high power makes the specimen look larger against the same scale, so each division then represents a smaller real distance.

How do I fit the graticule into my eyepiece?

Unscrew the top lens section of the eyepiece, lay the disc on the ledge of the field stop with the engraved side facing down, as most eyepieces require, and screw the lens back. If the lines look fuzzy, the disc is upside down or the eyepiece focus needs adjusting.

Can I measure with the graticule without calibrating it?

Only in relative terms. You can say that one cell spans eight divisions and another spans four, but you cannot express either in micrometres. Syllabus measurement tasks normally require the calibrated value.

How do I calculate a cell’s actual size?

Multiply the number of eyepiece divisions the cell spans by the calibrated value of one division for that objective. For example, a cell spanning 12 divisions, where each division is worth 2.5 micrometres, measures 30 micrometres across.

Which microscopes can take an eyepiece graticule?

Most eyepieces with an internal field stop can hold a disc of the right diameter, and some measuring eyepieces have a focusing top lens for sharper lines. Give your microscope model or eyepiece details in your enquiry so the diameter can be matched.

Last Updated: September 2026